WO2010038281A1

WO2010038281A1 - Zeolite separation membrane, process for producing the same, and binder

Info

Publication number: WO2010038281A1
Application number: PCT/JP2008/067797
Authority: WO
Inventors: 矢野　和宏; 高木　義信
Original assignee: 日立造船株式会社
Priority date: 2008-10-01
Filing date: 2008-10-01
Publication date: 2010-04-08
Also published as: US20110174722A1; CN102170962B; US9022226B2; EP2343115A4; CN102170962A; EP2343115A1

Abstract

A separation membrane characterized by comprising: a porous tube comprising alumina as the main component; a connection member disposed in a position for connection to the tube; a binder with which the connection member has been bonded to the tube and which is made of ceramic oxides comprising 17-48 wt.% SiO₂, 2-8 wt.% Al₂O₃, 24-60 wt.% BaO, and 0.5-5 wt.% ZnO as essential ingredients and containing at least one of La₂O₃, CaO, and SrO; and a thin zeolite layer formed on the surface of the porous tube. Before the zeolite layer is formed, the connection member is bonded to the porous tube. Thus, the binder can have a melting temperature exceeding the limit of up to 600°C, which is the heat-resistance limit to zeolite. This widens the choice of ceramic oxide compositions, e.g., glass compositions, to be used in the binder (there are no limitations on glass softening temperature).

Description

Zeolite separation membrane, method for producing the same, and bonding agent

The present invention relates to a zeolite separation membrane for separating a desired component from a liquid or gas mixture, and more specifically, used in an ethanol purification process in an ethanol production plant that uses a biomass raw material such as corn or sugar cane to produce fermentation. The present invention relates to a zeolite separation membrane used in an ethanol / water membrane separation device and a membrane separation device that removes water from a water-containing organic solvent to recover a high concentration organic solvent. The present invention also relates to a method for producing the separation membrane and a bonding agent used therefor.

The following known techniques are known as a method for joining or sealing pipes at one end of a zeolite separation membrane.

Patent Document 1 discloses a tube end connection structure including a member having elasticity or fluidity over each outer surface of one end of a ceramic tube with a zeolite membrane and one end of a metal tube to be connected thereto. Are listed.

Patent Document 2 discloses SiO ₂ : 15 to 20 wt%, Al ₂ O ₃ : 3 to 5 wt%, B ₂ O ₃ : A composition for sealing an inorganic separation membrane having a composition of 15 to 25 wt% and PbO: 55 to 65 wt% and a softening point of 400 to 600 ° C. has been proposed.

Patent Document 3 discloses a method in which an annular seal (O-ring / metal ring) is clamped by screwing a fixing member in order to close the end of the tubular separation member.

Patent Document 4 contains 55 to 65 mol% of silica, 1 to 10 mol% of zirconia, contains at least one alkaline earth metal oxide selected from the group of calcia, barrier and strontia, and contains zinc oxide. A ceramic porous body composed of an alkali-free glass that is substantially not contained has been proposed.
JP 2006-88079 A Japanese Patent Laid-Open No. 10-180060 JP 2005-313156 A JP 2006-263498 A

However, in the structure of Patent Document 1, a coating agent is used as a base of the coating material in order to cope with the shape roughness of the ceramic surface, and this coating material component elutes during operation of the apparatus and adversely affects the zeolite separation membrane. There is a risk. Further, the sealing work for applying the covering material at this time has a disadvantage that a relatively long working time and technical learning are required.

Regarding the seal of Patent Document 2, a glass composition containing a large amount of lead oxide is employed to soften and seal the glass at 600 ° C. or lower, and such lead oxide is eluted to the product side such as ethanol. There is a concern that damage to health and the environment may occur. Furthermore, since the glass seal is performed after the zeolite separation membrane is formed with respect to the structure of the joint, high adhesion between the glass and the joint interface is required at the joint. In particular, when the separation membrane and the gas conduit are joined, the cross-section of the separation membrane and the outer surface of the gas conduit are joined, so if the inner diameter of the separation membrane is larger than the outer diameter of the gas conduit, It is necessary to maintain the physical strength only by the seal portion, and in order to maintain a constant strength in this way, a considerably thick glass layer is required for the seal portion, and the amount of glass used becomes large.

In the method of Patent Document 3, since an O-ring (two locations) is used as a sealing member, the joining structure (screwed portion, O-ring clamping portion) at the end of the zeolite separation membrane is very complicated, and this part is manufactured. In doing so, a high degree of machining accuracy is required, and there is a problem that the cost increases.

In Patent Document 4, a ceramic porous body used for removing suspended substances, bacteria, dust, etc. mixed in a fluid with a ceramic porous body having a large number of pores is assumed, and an acid (citric acid solution) is assumed. ) Or a glass composition that does not contain zinc oxide in consideration of corrosion resistance to alkali (sodium hypochlorite aqueous solution), but the separation target is relatively large, and the glass evaluation for this is based on the foam pressure Therefore, strict glass elution is not discussed. Zeolite separation membranes that are separated by molecular size (angstrom) by a zeolite layer formed by crystal growth on a ceramic porous tube are slightly eluted by the hydrothermal reaction (heating and high alkali atmosphere) that forms the zeolite layer. Glass components affect zeolite crystal formation and reduce membrane performance (separation performance). In order to prevent this, it is necessary to find out the glass composition itself which has little influence on the formation of zeolite even if the glass component is eluted.

An object of the present invention is to provide a zeolite separation membrane, a method for producing the separation membrane, and a bonding agent used therefor, which have solved the above-mentioned problems associated with the prior art.

In the zeolite separation membrane according to the present invention, a porous tube composed of alumina as a main component and a joining member disposed at a joining position with the tube are composed of SiO ₂ : 17 to 48 wt%, Al ₂ O as an essential component. ₃ : fixed by a bonding agent made of ceramic oxide containing 2 to 8 wt%, BaO: 24 to 60 wt%, ZnO: 0.5 to 5 wt%, and containing at least one of La ₂ O ₃ , CaO and SrO The zeolite tube is formed on the surface of the porous tube.

In the zeolite separation membrane according to the present invention, the joining member is, for example, a sealing plug that seals at least one end of the ceramic porous tube, or a tube joined to at least one end of the ceramic porous tube.

In the zeolite separation membrane according to the present invention, it is preferable that the end portion of the joining member and the end portion of the ceramic porous tube are joined by fitting the concave portion and the convex portion as shown in FIG.

In the zeolite separation membrane according to the present invention, the thermal expansion coefficient of the joining member is preferably 4 to 9 × 10 ⁻⁶ (/ K) which is almost the same as that of the ceramic porous tube. If the thermal expansion coefficient of the joining member is different from that of the ceramic porous tube, the coating is cracked or peeled during firing to form a coating covering the outer surface of the joint.

In the zeolite separation membrane according to the present invention, the joining member preferably contains 50 wt% or more of alumina as a main component, has a vitreous ratio of 0.1 to 40 wt%, and has a crystal grain size of 1 μm or more. As a result, the joining member can have almost the same thermal expansion coefficient as that of the porous alumina tube used as the separation membrane, and leakage of ceramic oxide can be prevented in a highly alkaline atmosphere when forming the zeolite layer. Therefore, it is possible to prevent cracking due to heat at the joint surface between the joining member and the separation membrane, and to ensure physical strength as a zeolite separation membrane.

FIG. 1 is a photomicrograph showing particles of a sealing plug made of such a joining member, and FIG. 2 shows an example of measurement of particle diameter. Since the separation of the substance itself is performed in a separation membrane having a zeolite layer, it is necessary to avoid that the substance to be separated permeates through the joining member. By constructing a fine structure having a particle diameter (crystal particle diameter) of at least 1 μm or more after the bonding member is sintered, it is possible to prevent the substance to be separated from passing through the bonding member.

In the method for producing a zeolite separation membrane according to the present invention, a porous tube composed of alumina as a main component and a bonding member to be bonded to the tube are arranged at a bonding position, and SiO ₂ : 17 to 48 wt% as an essential component. Al ₂ O ₃ : 2 to 8 wt%, BaO: 24 to 60 wt%, ZnO: 0.5 to 5 wt%, and a junction made of a ceramic oxide containing at least one of La ₂ O ₃ , CaO and SrO An agent is interposed between the porous tube and the bonding member, and the bonding agent is baked to fix the porous tube and the bonding member, and then a zeolite layer is formed on the surface of the porous tube.

In the method for producing a zeolite separation membrane according to the present invention, the bonding agent is interposed between the porous tube and the bonding member in the form of a molded product of ceramic oxide powder or in the form of a slurry containing the oxide powder, It is preferable to fix the porous tube and the bonding member by baking the bonding agent.

The molded article of the ceramic oxide powder preferably contains a binder, or contains a binder and the binder is removed by firing after molding. The ceramic oxide powder molded product is such that the shape of the ceramic oxide powder is not lost by linking the ceramic oxide powder together with a binder. The molded product can be used by burning out the binder by heating, melting the glass, and maintaining the shape by melting the glass. Furthermore, since the heat treatment is performed when the ceramic porous tube and the bonding member are fixed, the heat treatment process can be reduced by burning the binder once formed by the binder by the heat treatment for bonding and fixing. It becomes possible.

In the method for producing a zeolite separation membrane according to the present invention, it is preferable to form a zeolite layer on the surface of the ceramic porous tube by hydrothermal synthesis.

Prior to the hydrothermal synthesis, it is preferable to attach the zeolite particles to the surface of the porous tube by immersing and drying the ceramic porous tube in a suspension in which the zeolite particles are suspended. In the method for producing a separation membrane according to the present invention, after a bonding member is fixed to the porous tube, a zeolite layer is formed on the surface of the porous tube. Even if a minute gap is generated at the joining boundary by immersing the joining surface of the porous tube and the joining member in a suspension of the zeolite particles that are the starting material for forming the zeolite layer, When a suspension of zeolite particles intrudes into the gaps and adheres the zeolite particles by drying, the zeolite layer that has crystal growth by the subsequent hydrothermal reaction fills the gaps, increasing the airtightness at the joint surface. Can do.

The bonding agent according to the present invention is a bonding agent for bonding a porous tube composed of alumina as a main component to a bonding member, and includes SiO ₂ : 17 to 48 wt%, Al ₂ O ₃ : 2 as essential components. It is characterized by comprising a ceramic oxide containing ˜8 wt%, BaO: 24-60 wt%, ZnO: 0.5-5 wt%, and containing at least one of La ₂ O ₃ , CaO and SrO.

The bonding agent according to the present invention may further contain 0.1 to 20 wt% of zirconia stabilized by yttria.

A typical example of ceramic oxide is glass. The molded article of ceramic oxide powder may be a ring, for example a glass ring.

In the method for producing a zeolite separation membrane according to the present invention, the joining member is fixed to the porous tube at a stage before forming the zeolite layer. As a result, the melting temperature of the bonding agent can exceed the limit of 600 ° C. or less, which is the heat resistance limit of zeolite, and the range of selection of the ceramic oxide composition used in the bonding agent, for example, the glass composition is widened (glass softening). There is no temperature limit).

Since the zeolite layer is formed on the surface of the porous tube after fixing the joining member to the porous tube, even if a minute gap occurs at the joining boundary, the zeolite layer will fill this gap. , The reliability of adhesion can be increased.

In addition, in the structure where the end of the joining member and the end of the ceramic porous tube are fitted, the physical strength can be brought about not only by the joining agent but also by the fitting. You can save.

The bonding agent according to the present invention contains SiO ₂ : 17 to 48 wt%, Al ₂ O ₃ : 2 to 8 wt%, BaO: 24 to 60 wt%, ZnO: 0.5 to 5 wt% as essential components, and La ₂ O ₃ , Since it is made of a ceramic oxide containing at least one of CaO and SrO, in the step of forming a zeolite layer by hydrothermal synthesis, when immersing the porous tube in which the bonding member is fixed with the bonding agent in a highly alkaline solution In addition, the components of the bonding agent do not dissolve in the same solution, and the bonding agent has no influence on the obtained zeolite layer.

In the present invention, a bonding agent containing no lead is used in consideration of health and the environment during the bonding work. Airtightness sufficiently corresponding to the roughness of the ceramic surface can be maintained without using a bonding agent containing components that may leak during the operation of the separation membrane and adversely affect the zeolite layer, or a coating material with complicated mounting work. .

By using the bonding agent and the bonding member having the above composition, the bonded portion between the zeolite separation membrane and the bonding member can have a simple structure, not only cost reduction but also mechanical strength and high airtightness that are the characteristics of ceramics. Can be held.

Next, in order to specifically explain the present invention, several examples of the present invention will be given.

Example 1
1) Adhesion of ceramic porous tube and joining member
(a) In FIG. 3, in order to seal the ceramic porous tube (1) (alumina 99%, outer diameter 16 mmφ, inner diameter 12 mmφ), one end of the tube (1) and the sealing plug (3) (dense A glass ring (2) obtained by compression-molding glass powder was interposed (see FIG. 3a). The composition of the glass powder used here is shown in B in Table 2. Next, this was fired at 900 ° C. for 1 hour to obtain a structure in which one end of the tube (1) was sealed.

(b) Thereafter, in order to improve the strength and hermeticity of the joint between one end of the ceramic porous tube (1) and the sealing plug (3), the joint is made of glass powder (composition: B in Table 2). ) Slurry (glass powder: 50 wt%, solvent: ethanol) and dried (see FIG. 3 b). Next, this was baked at 900 ° C. for 1 hour, thereby producing a structure in which the outer surface of the joint was covered with the glass coating (4).

2) Synthesis of Zeolite Separation Membrane In FIG. 4, a ceramic porous tube having a sealing stopper fixed to one end with glass as described above is used as a suspension of A-type zeolite crystal particles (Zeolam manufactured by Tosoh Corporation) (0.10 wt%). The end of the ceramic porous tube carrying the zeolite crystal particles was left at room temperature for 2 hours and then dried at 37 ° C. overnight. Next, these zeolite-supported ends were immersed in a reaction gel solution (composition Na ₂ O: SiO ₂ : Al ₂ O ₃ : H ₂ O = 88: 100: 4: 3960) at 100 ° C. for 4 hours. Hydrothermal synthesis was performed. By this hydrothermal synthesis, a zeolite membrane was formed on the outer surface of the ceramic porous tube.

The synthesized ceramic porous tube with zeolite membrane was washed with pure water and then dried at room temperature for one day and night.

Thus, the zeolite separation membrane shown in FIGS. 4 (a) and 4 (b) corresponding to FIGS. 3 (a) and 3 (b) was produced. In the figure, (1) is a ceramic porous tube, (3) is a sealing plug, (4) is a glass coating, (5) is a molten glass layer, and (6) is a zeolite layer.

The above zeolite separation membrane was subjected to an ethanol / water pervaporation test (PV test) under the following conditions. This test apparatus is shown in FIG. In the figure, (11) is a stirrer, on which a constant temperature bath (12) is placed, and a zeolite separation membrane (13) is placed in the water of the copper bath (12). (14) is a vacuum gauge, (15) is a trap by liquid nitrogen, (16) is a vacuum trap, and (17) is a vacuum pump.

PV test conditions: Effective membrane area 10.1cm ²
Ethanol / water = 90wt% / 10wt%
Reaction temperature = 75 ℃

The separation factor was determined according to the following formula.

Separation factor = (C _Water / C _EtOH ) _{permeation side} / (C _Water / C _EtOH ) _{supply side}
C _Water : Water concentration C _EtOH : Ethanol concentration

The test results obtained are as follows.

Fig. 4 (a) Zeolite separation membrane: Separation factor 9986
Fig. 4 (b) zeolite separation membrane: separation factor 1381
From this result, both the zeolite separation membrane of FIG. 4 (a) and the zeolite separation membrane of FIG. 4 (b) have a very high airtightness at the joint, and the seal has an influence on the zeolite separation membrane. It can be seen that it hardly affects.

Example 2
The effect of adding stabilized zirconia to glass powder was investigated by the following method.

In “1” Adhesion of ceramic porous tube and bonding material ”in Example 1, glass (composition: B in Table 2) was stabilized by yttrium as glass powder for bonding agent and glass powder for coating. Zeolite separation membrane was prepared in the same manner as in Example 1 except that a predetermined amount of zirconia (HYS-8 manufactured by Daiichi Rare Element Chemical Co., Ltd.) was added. An ethanol / water pervaporation test (separation factor) was performed on the membrane in the same manner as in Example 1.

The test results are shown in Table 1.

From this result, it can be seen that when the amount of stabilized zirconia added to the glass is 20 wt% or less, the performance (separation coefficient) of the zeolite separation membrane is higher than when no zirconium is added.

Example 3
The effect of glass powder composition on film performance was investigated by the following method.

In “1) Adhesion of ceramic porous tube and bonding material” in Example 1, the composition of the glass powder for bonding agent and the glass powder for coating was changed as shown in Table 2, and other than that in Example 1 The same operation was performed to produce a zeolite separation membrane. An ethanol / water pervaporation test (separation factor) was performed on the membrane in the same manner as in Example 1. The test results are shown in Table 3.

From this result, it can be seen that in the compositions A to D, the glass seal at the joint has a very high airtightness and a structure that hardly affects the zeolite separation membrane.

Example 4
The effects of the composition and thermal expansion coefficient of the joining member on the coating situation (adhesion and airtightness) were investigated by the following methods.

First, tubular joining members A to G having different compositions and thermal expansion coefficients were prepared. In FIG. 6, the former is cut so that one end of these joining members (21) can be inserted into one end of the inner diameter (φ12mm) of the alumina porous tube (1) (alumina 99.6%, outer diameter φ12mm). The small diameter part (21b) whose outer diameter is smaller than another part was formed in the edge part via the step part (21a). After inserting one end of the joining member (21) into one end of the alumina porous tube (1), a glass ring is formed between the step (21a) of the joining member (21) and the end surface of the alumina porous tube (1). (2) intervened.

Thereafter, the outer surface of the joint portion was covered with the glass coating (4) in the same manner as in “1) Fixing of the ceramic porous tube and the joint member” in Example 1. That is, after drying at 100 ° C. overnight, the sample was heated to 1000 ° C. at a temperature increase rate of 10 ° C./min and held at this temperature for 1 hour. Thereafter, it was allowed to cool to room temperature at a temperature lowering rate of 1 ° C./min. In this way, the structure shown in FIG. 6 was obtained. Thereafter, a zeolite membrane was formed on the outer surface of the ceramic porous tube by hydrothermal synthesis in the same manner as in “2) Synthesis of zeolite separation membrane” in Example 1. At this stage, the joint coating state was visually observed. The results are shown in Table 5.

As a result, when the thermal expansion coefficient of the joining member was different from that of the ceramic porous tube, cracking and peeling were recognized in the coating during firing to form a coating covering the outer surface of the joint. From this, the thermal expansion coefficient of the joining member is ^4-9 x 10 ^-6 (/ K), which is almost the same as that of the ceramic porous tube, contains 50 wt% or more of alumina as the main component, and the ratio of vitreous is It needs to be 0.1-40wt%.

An ethanol / water pervaporation test (separation factor) was performed on the membrane in the same manner as in Example 1. The test results are shown in Table 6. From this table, it can be seen that high separation performance is obtained with the joining members A to D, and that the composition of the joining member has little influence on the formation of the zeolite layer.

Example 5
7 (a) (b) (c) (d) show modified examples of the end structure of the ceramic porous tube and the end structure of the joining member. In the figure, (1) is a ceramic porous tube, (2) is a bonding agent, (3) is a sealing plug, (4) is a glass coating, (18) is a sealing cap, and (21) is a bonding member. .

A zeolite membrane was formed on the outer surface of the ceramic porous tube by hydrothermal synthesis in the same manner as in the step “2) Synthesis of zeolite separation membrane” in Example 1.

FIG. 1 is a photomicrograph showing particles of a sealing plug made of a joining member. FIG. 2 is a schematic diagram showing the measurement of the particle diameter of the sealing plug. FIGS. 3A and 3B are schematic views showing a fixing structure of the ceramic porous tube and the joining member. 4 (a) and 4 (b) are schematic views showing the synthesis of the zeolite separation membrane. FIG. 5 is a schematic view showing an apparatus for an ethanol / water pervaporation test (PV test). FIG. 6 is a schematic view showing a fixing structure of the ceramic porous tube and the joining member. 7 (a), (b), (c), and (d) are schematic views showing modifications of the end structure of the ceramic porous tube and the end structure of the joining member.

Explanation of symbols

(1) Ceramic porous tube (2) Glass ring (3) Seal plug (4) Glass coating (5) Molten glass layer (6) Zeolite layer (18) Sealing cap (21) Joining member

Claims

A porous tube composed of alumina as a main component and a joining member arranged at the joining position with the tube are, as essential components, SiO 2 : 17 to 48 wt%, Al 2 O 3 : 2 to 8 wt%, BaO : 24 to 60 wt%, ZnO: 0.5 to 5 wt%, and fixed on the surface of the porous tube by a bonding agent made of a ceramic oxide containing at least one of La 2 O 3 , CaO and SrO. A separation membrane comprising a thin layer.
The separation membrane according to claim 1, wherein the joining member is a sealing plug for sealing at least one end of the ceramic porous tube, or a tube joined to at least one end of the ceramic porous tube. .
2. The separation membrane according to claim 1, wherein an end of the joining member and an end of the ceramic porous tube are fitted.
2. The separation membrane according to claim 1, wherein the joining member has a thermal expansion coefficient of 4 to 9 × 10 −6 (/ K).
2. The separation membrane according to claim 1, wherein the joining member contains 50 wt% or more of alumina as a main component, the ratio of ceramic oxide is 0.1 to 40 wt%, and the crystal grain size is 1 μm or more.
A porous tube composed of alumina as a main component and a bonding member to be bonded to the tube are arranged at the bonding position. As essential components, SiO 2 : 17 to 48 wt%, Al 2 O 3 : 2 to 8 wt%, BaO: 24 to 60 wt%, ZnO: 0.5 to 5 wt%, and a bonding agent comprising a ceramic oxide containing at least one of La 2 O 3 , CaO and SrO is interposed between the porous tube and the bonding member A method for producing a separation membrane, comprising interposing and bonding a porous tube and a bonding member by firing a bonding agent, and then forming a zeolite layer on the surface of the porous tube.
The bonding agent is interposed between the porous tube and the bonding member in the form of a ceramic oxide powder molded product or in the form of a slurry containing the oxide powder, and the bonding agent is fired to form the porous tube. The method for producing a separation membrane according to claim 6, wherein the joining member is fixed.
8. The method for producing a separation membrane according to claim 7, wherein the molded product of ceramic oxide powder contains a binder, or the molded product contains a binder and the binder is removed by firing after molding.
When the zeolite layer is formed on the surface of the ceramic porous tube by hydrothermal synthesis, before the hydrothermal synthesis, the ceramic porous tube is dipped in a suspension in which the zeolite particles are suspended, and dried. The method for producing a separation membrane according to claim 8, wherein the is attached to the surface of the porous tube.
It is a bonding agent for bonding a porous tube composed of alumina as a main component and a bonding member. As essential components, SiO 2 : 17 to 48 wt%, Al 2 O 3 : 2 to 8 wt%, BaO: 24 A bonding agent comprising: 60 wt%, ZnO: 0.5 to 5 wt%, and comprising a ceramic oxide containing at least one of La 2 O 3 , CaO and SrO.
The bonding agent according to claim 10, further comprising 0.1 to 20 wt% of zirconia stabilized by yttria.